Stereoscopic projection map-making instrument



Dec.v27, 1949 H. TVKELSH 2,492,870

v STEREDSCOPIC PROJECTION MAP-MAKING INSTRUMENT Filed Jan. 20, 1948 sSheets-Sheet 1 HARRY T.K,ELSH

H. T- KELSH Dec. 21, 1949 swsnEoscorrc-nomcuon HAP-MAKING INSTRUMENTFiled Jan. 20, 1948 5 @heets-Sheet 2 :Z'I HARRY T. KELSH I"!- T. KELSH'STEREOSQOPIG PROJECTION llAP llAK Iflfi- INSTRUIENT 5 Sheets-Sheet 3Filld Jan. 20, 1948 o a a ac swan/WM HAR RY T. KELSH Dec; 1949 H. T.KELSH 2,492,870

STEREOSCOPIC PROJECTION'UAPMAKING INSTRUMENT Filed Jan. 20, 1948 5Sheets-Sheet 5 3mm HARRY T. KELSH mama Dec. 27, 1949 STEREOSCOPICPROJECTION MAP-MAKIN INSTRUMENT Barry '1. Keith, Washington, D. C.

Application January 20, 1948, Serial No. 3,263

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 4 Claims.

rms application is made under the act of March 3, 1883, as amended bythe act of- April 30, 1928, and the invention herein described, itpatented in any country, may be manuiactured and used by or for theGovernment or the United States of America for governmental purposesthroughout the world without the payment to me of any royalty thereon.

This invention relates to photogrammetry and is an improvement over theinstrument for making maps by stereophotogrammetric methods disclosed inmy copending application, Serial No. 669,772, filed May 15, 1946, nowPatent No. 2,451,031, dated October 12, 1948.

According to the invention of my copending application, a pair ofoverlapped standard size (9" by 9") slides (negatives taken byaeroplane, or transparencies made from them) are projected onto drawingpaper arranged on a drawing board either for visual inspection or formap-making purposes, a standard plotting table being used for drawingthe map. In general, according to that invention, the instrument isprovided with a. frame having two projection lanterns each having a lensand slide receiving means and sup= ported side by side on the frame forprojecting images of a pair of consecutive slides on a screen. Lightfiltering devices such as complementary color filters or polarizers areso arranged that the superimposed images may be viewed through glassescoloredto match the color filters or through polarizer glasses to show astereoscopic model, so that the drawing paper may be placed on the maptable as a screen and the model cast on the drawing paper, or cast onthe screen oi a standard movable plotting table and topographic andplanimetric maps drawn in the regular manner. The parts are soconstructed and arranged, especially as to adjustment, that a model ofdegree of fineness required for work of this kind is obtained; 4

In that instrument, the light for each lantern is provided by a pointlight source and light con denser so arranged that the light convergesthrough substantially the entire area of the slide, thence through thenodal point of the lens and diverges to cover substantially the entirearea of the map drawing paper. This requires a light of considerablecandle power, and due to the large divergence of the light, the lightintensity on the drawing paper varies materially, being less intense atthe edges.

It is the object of the present invention to provide an instrumentemploying a lesser candle power lighting system and yet maintain ample 2illumination for map-making purpose, and giving greater uniformity oflight intensity over the area necessary to be viewed.

In drawing maps with a plotting table, the only area which need beviewed at any particular time is the small area of the plotting tablescreen on which the stereoscopic model is viewed. In general, accordingto the present invention, a small point light source and alightcondenser are provided for each lantern, the light source vand lightcondenser being so arranged as to converge'the light through only asmall area of the slide and thence through the nodal point of the lens,and diverge the light onto a small area sufllcient substantially tocover the screen of the plotting table. The light source and lightcondenser are movable, however, in such manner that substantially theentire area of the slide may be traversed by the converging light rays.The means for moving each light source is attached to the plotting tableso that as the plotting table is moved about on the drawing paper, thelight source and condenser move in a manner to maintain the image on thescreen of the plotting table and to maintain the point of convergence ofthe light rays coincident with the nodal point of the lens.

For a detail description of the invention, reference is made to theaccompanying drawing. in which:

Figure 1 is a front elevation of the instrument with parts broken awayfor clarity in illustration;

Figure 2 is a section on line 2-2 oi Figure 1;

Figure 3 is an enlarged longitudinal section of the lens;

Figure 4 is a section on line M of Figure 1:

Figure 5 is a section on line E-E of 4;

Figure 6 is a three-dimensional view showing a portion of the instrumentto illustrate the manher of mounting the light;

Figures 7, 8, 9 and 10 are three-dimensional views of details usedwiththe assembly shown in Figure 6;

Figure 11 is a three-dimensional view of the plotting table with partsbroken away to illustratethe manner of connecting the means for movingthe light to the plotting table; and

Figure 12 is a section on the line [2-42 of Figure 11. Q

In the drawing, the main frame ll of the instrument is provided with anupright at each corner, the front two of which are shown at I! and 13 ofFigure 1. A horizontal platform I! is vertically slidably mounted on.the uprights and adjusted by knurled adjusting nuts I. and il threadedon the uprights, a drawing board ll \Rflng adjustably mounted on theplatform by adjusting-screws as shown at I 8 and 28. A central open,rectangular cross frame, the front side member of which is shown at 2|,and an upper open, rectangular cross frame, the front side member ofwhich is shown at 22. the back side members being shown at 28 and. 28,respectively, are rigidly fixed to the uprights.

A pair of projection lanterns 25 and 28 are suitably adiustablysupported on the frame to cast superimposed images from-a pair ofconsecutive slides onto the screen of the plotting table. These lanternsare similar, except that one is arranged at the left hand and the outerat the right hand, the position of the parts corresponding, and thecolor filter in one is complementary t that of the other, or in case ofthe use of polarizers, one polarizer is normal to the other, and onllantern 28 and its supports and adjustments will be described in detail.

Lantern 26 is supported on an open, rectangular lantern'supportingframe, the front and righthand side members being shown at 21 and 28,re-

spectively, the lantern frame being horizontally front one of saidlast-mentioned uprights being shown at 30. Vertical adjustment of thelantern is obtained by sprocketed nuts, the front two being shown at 3|and 32, threaded on the uprights, these nuts being simultaneouslyoperated by a continuous loop chain 38 engaging the nut sprockets.

The slide 40 is removably supported on an open, rectangular slidesupporting frame 4| which in turn is carried by legs l2, 43, 44 and 45at its corner, these legs being rigidly attached to an apertured bottom46. Bottom 45 is provided with downwardly extending tits 81 and 48 whichare slidable in mating grooves 49 and 50 arranged on a circle in an openbottom supporting member thus to provide for partial rotation of bottom46 and slide 40 to compensate for crab of the aeroplane in taking thesnapshot. The bottom 46 is held in place by spring clips 52 and 53 andis rotated by a sector 5| of gear teeth driven by a gear 55 attached toone end of a drive shaft 56 rotatably mounted in supporting member 5I.The other end of the drive shaft is provided with a. gear 51 fixedthereto which may be manuall rotated by means of a thumb screw 58, theshaft of which is also rotatably mounted in the member 5|, driving agear 59 mating with gear 51, thus to angularly adjust the slide. Member5| is provided with laterally projecting pivot pins 50 and GI whichengage in suitable sockets 62 and 63 provided in opposite sides of anopen, rectangular frame member 5|. This provides for tilting the lanternto compensate for tilt of. the aeroplane in taking the snapshots. Member5| is tilted by means of a manually operated thumb screw 55 having aspherical tip 65 engaged in a mating socket in member 54 and threadedthrough a lug il fixed to an open rectangular frame member 58.

,Member 54 in turn is provided with pivot pins and II projecting normalto pivot pins 80 and SI and engaging in suitable sockets I2 and I3provided in opposite sides of the frame member 88, the member 64 beingcaused to pivot by operation of a manually operated thumb screw I5having a spherical tip I8 engaging in a mating socket in member 54,thumb screw "I5 being threaded through a lug II fixed to member 88. Thisad- Justment compensates for tip of the aeroplane in taking thesnapshots.

Frame member 68 is mounted on rollers 88, ll. 82 and 83 which ride onside members It and 85 of an open, rectangular frame member 88 thus toprovide for lateral adjustment of the lantern relative to the otherlantern, member 08 beinl moved in making this adjustment by means of tnormally operated thumb screw 81 threaded through lug 88 fixed to member85 and having its tip pivoted on a lug 89 fixed to member 88.

Frame member 86 is mounted on rollers, the front two of which are shownat and 8|, which ride on the front and back members 21 and 82 of thelantern supporting frame thus to provide ad- Justment of the lanterntoward or away from the other lantern. Member is moved by thumb screw 93threaded in side member 28 and having its tip rotatably mounted in sidemember 85 of frame member 88. The general arrangement of parts andadjustments thus far described is generally similar to that described inmy copending application above referred to. The particular features ofnovelty in the present invention over the copending application relateto the lens, the light and light condenser, the plotting table, and themanner in which these parts are related to each other.

The lens I00 itself, shown in detail in Figure 3,

is of a usual construction. This lens is fixedly mounted in a bracketI0| which in turn is fixed to the bottom supporting member 5|, as bestshown in Figure 6. Thus it will be noted that the lens partakes of allthe adjustments above described, except that to compensate for crab ofthe aeroplane.

The light bulb 103 is a small size commercial type bulb, designed togive substantially a point light source, mounted in a socket I04suitably supported in a casing I05, 3. small light condenser I06 beingprovided to converge the light rays through a polarizer I01 and to apoint. The casing I05 is fixed to one end of a light-supporting bracketII 0 which is universally mounted relative to the lens at its other endto member 5| in such manner that the light in converging passes. througha small area of the slide 40 and its point of convergence coincides withthe nodal point of the lens, regardless of any adjustments of theinstrument or movement of the light. Further-' more, angular adjustmentof the lanterns to compensate for crab does not disturb the lens and thelight or its mounting parts. Consequently, =polarizers may be used as atI01 and when properly adjusted normal to each other, adjustment for crabdoes not afiect them.

For the purpose of this universal mounting, a small open, rectangularframe member 5 is pivoted on pins I I6 and 1 inside the opening throughmember 5| for swinging on a pivot line containing the nodal point of thelens, and bracket IIII is pivoted on pins I I8 and I9 for swinging on apivoted line normal to the pivoted line of H6 and I I1 and alsocontaining the nodal point of the lens.

The bracket I|0 being offset in the manner illustrated is provided witha counterweight I20 to obtain balance.

A usual type plotting table best shown in Figures 11 and 12, as providedwith the usual base I25 carrying a stylus I26, with upright standardsI21 and I28 slidably mounting the plotting table screen I 29, and withan adjusting screw I30 for vertical adjustment of the screen. Means formoving the lights is so attached to the plotting table that as the tableis moved about the imagecast upon the screen from each light remains onthe screen. This is accomplished by provision of a cross bar I32rotatably mounted on'the plotting table and telescoping rods I33 and I34universally attached at their lower end to ends of bar I32 and fixedlyattached at their upper ends to the light supporting bracket I35 and Hof the lantern 25 and 26, respectively, the arrangement being such thatthe line through the point light source and the nodal point of the lensof each lantern falls approximately on the center of the plotting tablescreen.

It will thus be seen that, with a pair of consecutive slides properlypositioned in the lanterns and proper adjustments of the lantern to givea clear stereoscopic model on the plotting table screen when viewedthrough color filters such as polarizer glasses, the plotting table maybe moved about at will and the lights will so move that the image fromdifierent small areas of the slides will always be cast on the screen,thus accomplishing the purposes of this invention.

Having thus described the invention, what is claimed is:

1. An instrument for making maps by stereophotogrammetrio methods,comprising a pair of projection lanterns each having a lens andslidereceiving means and supported side by side for projectingsuperimposed images of a pair of consecutive slides, a movable plottingtable having a screen on which the images are projected for viewing togive a stereoscopic model, a point light source for each lantern and alight condenser to converge the light rays through a small area of theslide and to a point coincident with the nodal point of the lens anddiverge the light rays to cover approximately the screen of the plottingtable, each of said light source and light condenser being movablymounted relative to the lens in such manner that substantially theentire area of the slide in each lantern may be traversed by theconverging light rays, and means for movin each light source and itslight condenser so attached to the plotting table that, as the plottingtable is moved about, the light source and condenser move in a manner tomaintain the image on the screen and to maintain the point ofconvergence of the light rays coincident with the nodal point of thelens.

2. A stereoscopic projection apparatus comprising a pair of projectionunits having each a diapositive mount, a movable light beam projectorand a projection lens, a movable mapping table having a projectionscreen, a linkage system connecting said table to said projectors so asto constrain the movements of the projectors in response to movements ofthe table so that the projectors will each swing in an are about thenodal region of its projection lens and light from .irom said projectorsto substantially the area of i said screen.

3. A stereoscopic projection apparatus comprising a pair of projectionunits having each a diapositive mount, a movable light beam projectoranda projection lens, a movable mapping table having a projection screen, alinkage system connecting said table to said projectors so as toconstrain the movements of the projectors in response to movements ofthe table so that the projectors will each swing in an are about itscorresponding projection lens at a predetermined radius from the nodalregion of the lens and light from the projectors will pass through saidnodal regions onto said screen, and means, including said projectionlenses, for limiting the spread of light from said projectors tosubstantially the area of said screen.

4. A stereoscopic projection apparatus comprising a pair of projectionunits having each a diapositive mount, a movable light beam projectorand a projection lens, a movable mapping table having a projectionscreen, a linkage system connecting said table to said projectors so asto constrain the movements of the projectors in response to movements ofthe table so that the projectors will each swing in an are about itscorresponding projection lens at a predetermined radius from the nodalregion of the lens and light from the projectors will pass through saidnodal regions onto said screen, means for adjustin the length of thesaid radius, and means, including said projection lenses for limitingthe spread of light from said projectors to substantially the area ofsaid screen.

HARRY T. KELSH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITEl STATES PATENTS Number Name Date 1,199,460 Featherstone Sept. 26,1916 1,655,306 Barr et a1 Jan. 3, 1928 1,980,657 Bauersfeld Nov. 13,1934 1,980,981 Cooke Nov. 20, 1934 2,022,366 Boecking Nov. 26, 19352,023,970 Newman Dec. 10, 1935 2,085,498 Horner June 29, 1937 2,164,847Trautmann July 4, 1939 2,187,803 Grifiln Jan. 23, 1940

